Marine vessels such as tugboats are often used to tow or push other marine vessels in harbors, over the open sea, or through rivers and canals. They are also used to tow barges, disabled ships, or other equipment. Such vessels are typically powered by an on-board thermal prime mover, e.g., one or more diesel engines. A common propulsion system includes a pair of relatively large, high power, e.g., 2000 plus horsepower, diesel engines.
Tugboats, however, have widely varying propulsion loads. That is, propulsion of tugboats is often characterized by long periods of low power punctuated by shorter periods of high power propulsion. When undertaking low power tasks, dedicated high power propulsion engines rarely operate at peak engine efficiencies. This may result in the engine emitting greater amounts of pollutants such as carbon dioxide, and/or consuming more fuel, than if the engine was operating at a higher level of efficiency. Also, the larger the diesel engine, the more space required to house the engine in the tugboat.
In many tugboats, diesel engines provide electrical power both for propulsion and for powering various on-board service or auxiliary loads, such as, for example, a motor for moving a tow winch. The electrical power is produced at a constant, fixed frequency, typically 50 or 60 Hz. In many systems, a separate additional pair of auxiliary engines is employed to generate constant frequency electrical power, for a total of four engines. As will be appreciated, the greater the number of on board engines, the greater amount of space required, in addition to increased fuel consumption, emissions, and maintenance costs.
It may be desirable, therefore, to provide a system and method for powering a marine vessel, other vehicle, or other engine-driven platform that differ from existing systems and methods.